1. Field of the Invention
The present invention relates to a telecommunication beam receiving or emitting antenna.
In particular, the antenna is intended for domestic installations in individual houses, for collective installations in buildings, or for community installations serving to feed the heads of cable networks for receiving plural beams emitted by telecommunication satellites, notably carrying television signals.
In addition, the invention can be used for professional applications notably in data communication networks.
2. Description of the Prior Art
The currently most widely sold antenna for satellite reception on the market comprises a fixed reflector of which the reflecting surface is a paraboloid of revolution, or an elliptical paraboloid, approximately 90 to 120 cm wide, or a portion of such a paraboloid for an antenna with off-axis illumination, referred to as an offset antenna. The axis of symmetry of the reflector is pointed towards the satellite whose transmissions are to be picked up. A microwave reception head, usually fastened by stays, is positioned at the single focus of the paraboloid reflector.
When the aforesaid satellite has an orbital position very close to other geostationary satellites, e.g. such as the TDF 1, OLYMPUS and TV SAT 2 satellites situated at 19.degree. longitude west, the antenna can pick up the beams of these different satellites.
If the user wishes to receive beams from another satellite having an orbital position different to that of the abovementioned satellites, e.g. located at longitude east, the reflector of the receiving antenna must be turned around to be pointed to this other satellite. There are two solutions: either the user climbs onto the roof of a house or building in order to manually position the reflector, or the antenna must comprise remote-controlled motorized means for orientating the reflector.
In practice, the first solution is very rarely implemented by the user in view of the difficulty in gaining access to the antenna. It therefore requires recourse to an installation expert and a further adjusting of the position of the reflector, and is therefore highly dissuasive for the user.
The second solution is penalized by the cost of the antenna and its installation, an antenna with a motorized reflector requiring an infrastructure that is heavier and more cumbersome.
Other antennae are flat and are based on the FRESNEL lens principle (German patent applications Nos. 3,536,348 and 3,801,301) in order to remedy the high cost and unsightly appearance of parabolic antennae. However, these antennae also have a single focus and therefore a single pointing direction.